132 TECHNICAL BULLETIN 4. 



14. Sugar in the media greatly increases the growth. The same sub- 

 stance probably accounts for its rapid growi^h in the host. 



15. Starch furnishes a very poor source of carbon. 



16. Decoctions from soil or manure furnish all the essentials for growth. 



17. A small amount of acid checks its growth. 



18. Freezing does not kill the mycelium. 



19. No sporidia (conidia) have been found by the WTiter in pure cul- 

 tures or in soil. 



20. The mycelium at an early stage breaks up into short ])lump cells 

 which have all the functions of sporidia and are probably of great im- 

 portance in dissemination. 



21. The organism gets into the soil either by means of spores when the 

 sorus is broken up, or as mycehum which grows from the lesions when in 

 contact with moist soil. 



22. Infection occurs during the time from the second day after the 

 seed germinates until about the time that the first leaf appears on the side 

 of the cotyledon, after which the plant is immune. 



23. Infection occurs only through the cotyledon, and any part of its 

 epidermis may serve as the point of infection. 



24. The infecting hypha bores directly through the outer wall of the 

 epidermal cell, forms a hyphal gnarl inside the cell, and then passes 

 through the inner wall into the intercellular spaces where it grows during 

 the rest of its development. 



25. Many infections may occur on the same cotyledon. 



26. The incubation period is less than a week. 



27. Large complicated haustoria are formed within the host cells. 



28. An infected plant recovers if the fungus fails to reach the growing 

 zone; but if it once becomes established in this zone, the plant never 

 recovers, and most if not all the leaves will contain lesions. 



29. At the close of the incubation period the mycelium is in dense masses 

 between the cells, and from this the spores develop in sori. 



30. The spore begins as a recurved lateral or terminal branch, forming a 

 crozier, circle or short spiral. 



31. Branches arising from the circle (crozier) form a close covering 

 about the terminal (fertile) cell. 



32. By adhesion of the cells of the covering hyphse and rapid expansion 

 of the fertile cell the enclosing hyphce are separated into the scattered 

 elements which appear as the sterile ceUs of the mature spore. 



33. The fertile cell contains a single, large nucleus, and each sterile cell 

 a single small nucleus. Probably the large nucleus is a result of fusion. 



VIII. Literature Cited. 



(1) Baiy, A. de. Untersuchungen ilber die Brandpilze. Berlin. 1853. 



(2) Bary, A. de. Comp. Morph. and Biol., etc. 1887. 



(3) Brefeld, O. Untersuch. a. d. Gesam. Myk. 5. 



(4) Ibid. Vol. 12. 



